ABSTRACT: Measurements of the spectral scattering and attenuation properties of coccolithophores (Emiliania huxleyi; clone 88E) and their associated coccoliths were made for three growth phases a< well as for acidified cultures. These measurements allow a clean separation and determination of the optical effects of the various components. The beam attenuation cross sections (m2 particle-l) were found to be 8.4E-12, 2.6E-10, and 4.9E-11 for coccoliths, plated cells, and naked cells, respectively, at 440 nm. The spectral dependence of these factors followed a power law dependence, with a wavelength exponent of - 1.9, 0.42, and -0.52 for the coccoliths, plated cells, and naked cells. The volume scattering functions for all appeared similar; however, the backscattering cross sections (m2 particle-) at 456 nm were 1.4E-13, 6.7E-12, and 9.9E-13, respectively. The wavelength dependence of this parameter also followed a power law and was - 1.4, - 1.2, and - 1.0. Overall, these results show that optical properties of a coccolithophore bloom are sensitive to the coccolith : cell ratio and can vary between and within blooms.

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